package com.cxp.springboot2rsaaes.RSAandAES.utils;


import org.apache.commons.codec.binary.Base64;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.*;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;

/**
 * @author 程
 * @date 2019/7/15 上午8:48
 */
public class TestRSA {

    /*RSA最大加密明文大小*/
    private static final int MAX_ENCRYPT_BLOCK = 117;

    /*RSA最大解密密文大小*/
    private static final int MAX_DECRYPT_BLOCK = 128;

    public static KeyPair getKeyPair() throws Exception {
        KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
        generator.initialize(1024);
        return generator.generateKeyPair();
    }

    /**
     * 获取私钥
     *
     * @param privateKey 私钥字符串
     * @return
     */
      public static PrivateKey getPrivateKey(String privateKey) throws Exception {
          KeyFactory keyFactory = KeyFactory.getInstance("RSA");
          byte[] decodedKey = Base64.decodeBase64(privateKey.getBytes());
          PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(decodedKey);
          return keyFactory.generatePrivate(keySpec);
      }

              /**
        * 获取公钥
        *
        * @param publicKey 公钥字符串
        * @return
        */
              public static PublicKey getPublicKey(String publicKey) throws Exception {
                 KeyFactory keyFactory = KeyFactory.getInstance("RSA");
                 byte[] decodedKey = Base64.decodeBase64(publicKey.getBytes());
                 X509EncodedKeySpec keySpec = new X509EncodedKeySpec(decodedKey);
                 return keyFactory.generatePublic(keySpec);
             }

              /**
        * RSA加密
        *
        * @param data 待加密数据
        * @param publicKey 公钥
        * @return
        */
              public static String encrypt(String data, PublicKey publicKey) throws Exception {
                  Cipher cipher = Cipher.getInstance("RSA");
                  cipher.init(Cipher.ENCRYPT_MODE, publicKey);
                  int inputLen = data.getBytes().length;
                  ByteArrayOutputStream out = new ByteArrayOutputStream();
                  int offset = 0;
                  byte[] cache;
                  int i = 0;
                  // 对数据分段加密
                  while (inputLen - offset > 0) {
                      if (inputLen - offset > MAX_ENCRYPT_BLOCK) {
                          cache = cipher.doFinal(data.getBytes(), offset, MAX_ENCRYPT_BLOCK);
                      } else {
                          cache = cipher.doFinal(data.getBytes(), offset, inputLen - offset);
                      }
                      out.write(cache, 0, cache.length);
                      i++;
                      offset = i * MAX_ENCRYPT_BLOCK;
                  }
                  byte[] encryptedData = out.toByteArray();
                  out.close();
                  // 获取加密内容使用base64进行编码,并以UTF-8为标准转化成字符串
                  // 加密后的字符串
                  return new String(Base64.encodeBase64String(encryptedData));
              }

              /**
        * RSA解密
        *
        * @param data 待解密数据
        * @param privateKey 私钥
  0      * @return
  1      */
              public static String decrypt(String data, PrivateKey privateKey) throws Exception {
                 Cipher cipher = Cipher.getInstance("RSA");
                 cipher.init(Cipher.DECRYPT_MODE, privateKey);
                 byte[] dataBytes = Base64.decodeBase64(data);
                 int inputLen = dataBytes.length;
                 ByteArrayOutputStream out = new ByteArrayOutputStream();
                 int offset = 0;
                 byte[] cache;
                 int i = 0;
                 // 对数据分段解密
                 while (inputLen - offset > 0) {
                         if (inputLen - offset > MAX_DECRYPT_BLOCK) {
                                 cache = cipher.doFinal(dataBytes, offset, MAX_DECRYPT_BLOCK);
                             } else {
                                 cache = cipher.doFinal(dataBytes, offset, inputLen - offset);
                             }
                         out.write(cache, 0, cache.length);
                         i++;
                         offset = i * MAX_DECRYPT_BLOCK;
                     }
                 byte[] decryptedData = out.toByteArray();
                 out.close();
                 // 解密后的内容
                 return new String(decryptedData, "UTF-8");
             }

             /**
       * 签名
       *
       * @param data 待签名数据
       * @param privateKey 私钥
       * @return 签名
       */
             public static String sign(String data, PrivateKey privateKey) throws Exception {
                 byte[] keyBytes = privateKey.getEncoded();
                 PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(keyBytes);
                 KeyFactory keyFactory = KeyFactory.getInstance("RSA");
                 PrivateKey key = keyFactory.generatePrivate(keySpec);
                 Signature signature = Signature.getInstance("MD5withRSA");
                 signature.initSign(key);
                 signature.update(data.getBytes());
                 return new String(Base64.encodeBase64(signature.sign()));
             }

             /**
       * 验签
       *
       * @param srcData 原始字符串
       * @param publicKey 公钥
       * @param sign 签名
       * @return 是否验签通过
       */
             public static boolean verify(String srcData, PublicKey publicKey, String sign) throws Exception {
                 byte[] keyBytes = publicKey.getEncoded();
                 X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
                 KeyFactory keyFactory = KeyFactory.getInstance("RSA");
                 PublicKey key = keyFactory.generatePublic(keySpec);
                 Signature signature = Signature.getInstance("MD5withRSA");
                 signature.initVerify(key);
                 signature.update(srcData.getBytes());
                 return signature.verify(Base64.decodeBase64(sign.getBytes()));
             }

             public static void main(String[] args) {
                 try {
                         // 生成密钥对
                         KeyPair keyPair = getKeyPair();
                         String privateKey = new String(Base64.encodeBase64(keyPair.getPrivate().getEncoded()));
                         String publicKey = new String(Base64.encodeBase64(keyPair.getPublic().getEncoded()));
                         System.out.println("私钥:" + privateKey);
                         System.out.println("公钥:" + publicKey);
                         // RSA加密
                         String data = "待加密的文字内容";
                         String encryptData = encrypt(data, getPublicKey(publicKey));
                         System.out.println("加密后内容:" + encryptData);
                         // RSA解密
                         String decryptData = decrypt(encryptData, getPrivateKey(privateKey));
                         System.out.println("解密后内容:" + decryptData);

                         // RSA签名
                         String sign = sign(data, getPrivateKey(privateKey));
                         // RSA验签
                         boolean result = verify(data, getPublicKey(publicKey), sign);
                         System.out.print("验签结果:" + result);
                     } catch (Exception e) {
                         e.printStackTrace();
                         System.out.print("加解密异常");
                     }
             }
}
